THE THORAX 1055 



bronchus are to be observed, and it is to be specially noted that the right 

 bronchus is more in line with the trachea than the left. The trachea is then 

 to be carefully divided a little above its bifurcation, and the lower part of it, 

 with the two bronchi and two lungs, is to be removed. The right bronchus 

 is to be dissected, and its eparterial and hypaxterial divisions are to be shown. 

 The ramifications of the bronchial tubes within the lungs are then to be 

 followed out. 



The difference bet^veen the main bronchus and its pulmonary ramifica- 

 tions, as regards the extent of the cartilaginous rings in their walls, should 

 attract attention. The bronchial tubes are to be laid freely open, and their 

 mucous lining is to be inspected. The lung is also to be incised at different 

 parts, and the cut surfaces examined. A portion of healthy lung should be 

 put into a dish of water, and the result should be noted. 



The thoracic part of the oesophagus is next to be displayed. The dissector 

 is to note that it lies at first on the right side of the descending aorta, 

 then in front of it, and finally slightly to its left side. The right and left 

 pneumogastric nerves will be found in very close contact with the gullet, 

 the right nerve gradually inclining from the right side of the tube to its pos- 

 terior aspect, and the left nerve gradually inclining from the left side of the 

 tube to its anterior aspect. The plexus gulae, formed by branches of these 

 two nerves, should be displayed, and the oesophageal branches of the descend- 

 ing aorta are to be borne in mind. 



The oesophagus is to be displaced, and the thoracic duct is to be dissected. 

 The dissectors should remember that this duct is sometimes double in the 

 thorax. It \%-ill be found lying close to the right side of the descending aorta, 

 between it and the right azygos vein. It is to be carefully followed up 

 beneath the arch of the aorta and along the left side of the oesophagus, on 

 its way to the root of the neck on the left side. The dissectors of the thorax 

 should now associate themselves with the dissectors of the head and neck, 

 in order to follow the thoracic duct to its termination in the angle of junction 

 between the left internal jugular and left subclavian veins. 



The descending aorta falls to be dissected next, along with its branches. 

 The aortic intercostal arteries are to be shown on either side, and they are 

 to be followed into the back parts of the intercostal spaces. At this stage 

 the dissector should display the delicate posterior intercostal aponeurosis 

 between which and the parietal pleura each intercostal artery passes. The 

 corresponding intercostal vein and nerve are to be shown in position, and 

 near the angle of the rib the aortic intercostal artery will be found to give 

 off its collatercil intercostal branch, having previously, on its entrance into 

 the space, given off its dorsal branch. In dissecting the descending aorta 

 the bronchial arteries which nourish the lungs are to be looked for behind 

 the corresponding bronchus. There' is usually one right bronchial artery, 

 which arises either from the descending aorta or from the first right aortic 

 intercostal artery, and there are two left bronchial arteries, which spring 

 from the parent trunk. 



The azygos veins are next to receive attention. The right azygos vein 

 will be found under cover of the oesophagus, where it has the thoracic duct 

 on its left side, and it is to be followed up to its termination in the superior 

 vena cava, a tag of which vessel has been specially preserved. The following 

 tributaries are to be shown enteiing the right azygos vein : (1) the lower 

 seven, or it may be eight, right intercostal veins ; (2) the lower and upper 

 transverse azgyos veins ; and (3) the right superior intercostal vein, which 

 takes up the second and third, and it may be the fourth, intercostal veins 

 of the right side. The first right intercostal vein opens into the correspond- 

 ing innominate vein, or sometimes into the vertebral vein. The lower and 

 upper left azygos veins are then to be dissected, along with the lower and 

 upper transverse azygos veins ; and the left superior intercostal vein, if not 

 previously dissected, is to be followed over the back part of the arch of the 

 aorta, and shown entering the left innominate vein. The first left intercostal 

 vein is disposed similarly to its feUow of the right side. 



The superior intercostal artery on either side is to be dissected, and its 



